Contamination and health risks from heavy metals in cultivated soil in Zhangjiakou City of Hebei Province, China.

A total of 79 topsoil samples (ranging from 0 to 20 cm in depth) were collected from a grape cultivation area of Zhangjiakou City, China. The total concentrations of As, Cd, Hg, Cr, Cu, Mn, Ni, Pb, and Zn in soil samples were determined to evaluate pollution levels and associated health risks in each sample. Pollution levels were calculated using enrichment factors (EF) and geoaccumulation index (I geo). Health risks for adults and children were quantified using hazard indexes (HI) and aggregate carcinogenic risks (ACR). The mean concentrations of measured heavy metals Cd, Hg, and Cu, only in the grape cultivation soil samples, were higher than the background values of heavy metals in Hebei Province. According to principal component analysis (PCA), the anthropogenic activities related to agronomic and fossil fuel combustion practices attributed to higher accumulations of Cd, Hg, and Cu, which have slightly polluted about 10-40% of the sampled soils. However, the HI for all of the heavy metals were lower than 1 (within safe limits), and the ACR of As was in the 10(-6)-10(-4) range (a tolerable level). This suggests the absence of both non-carcinogenic and carcinogenic health risks for adults and children through oral ingestion and dermal absorption exposure pathways in the studied area. It should be also noted that the heightened vulnerability of children to health risks was accounted for higher HI and ACR values. Consequently, heavy metal concentrations (e.g., Cd, Hg, Cu) should be periodically monitored in these soils and improved soil management practices are required to minimize possible impacts on children's health.

Health risk assessment of heavy metals for edible parts of vegetables grown in sewage-irrigated soils in suburbs of Baoding City, China.

With the long-term application of wastewater to vegetable production fields, there is concern about potential health risks of heavy metals contaminating the edible parts of vegetables grown in contaminated soils in the suburban areas of Baoding City, China. The average concentration of elemental Zn in sewage-irrigated soil was the highest (153.77 mg kg(-1)), followed by Pb (38.35 mg kg(-1)), Cu (35.06 mg kg(-1)), Ni (29.81 mg kg(-1)), and Cd (0.22 mg kg(-1)) which were significantly higher (P < 0.05) than those in the reference soil. The results showed that long-term sewage irrigation had led to a growing accumulation of heavy metals in the soils, especially for Cd, Zn, and Pb. Furthermore, the concentrations of elemental Cd, Zn, and Ni in vegetables (e.g., Beassica pekinensis L., Allium fistulosum L., Spinacia oleracea L.) collected from the wastewater-irrigated soils exceeded the maximum permissible limits, and this also increased the daily intake of metals by food. However, compared with the health risk index of <1 for heavy metals, the ingestion of vegetables from the soils irrigated with sewage effluent posed a low health risk. Nevertheless, heavy metal concentrations should be periodically monitored in vegetables grown in these soils together with the implementation effective remediation technologies to minimize possible impacts on human health.

[Effects of foliar spraying with low concentration NaCl on the growth and physiological responses of cucumber seedlings under temperature regulation in solar greenhouse]. / 设施调温模式下叶施低浓度NaClå¯¹é»„ç“œå¹¼è‹—ç”Ÿé•¿å’Œç”Ÿç†æŒ‡æ ‡çš„å½±å“.

In order to clarify the effects of foliar spraying the solution with low concentration NaCl on the growth and matter accumulation of vegetables under the temperature-regulated solar greenhouse, we carried out an experiment on cucumber seedlings with two cotyledons, under two tempera-ture regimes and four concentrations of NaCl. Low-medium temperature zone (L) and medium-high temperature zone (H) were set by low tunnel with plastic film in the greenhouse. The solutions with different concentrations of NaCl, 0 mmol·L-1 (L0 and H0), 5 mmol·L-1 (L5 and H5), 10 mmol·L-1 (L10 and H10) and 15 mmol·L-1 (L15 and H15), were sprayed every day to the cucumber seedlings. The seedling growth, plant biomass, nutrient accumulation and photosynthetic gas exchange parameters of cucumber seedlings were measured at the 21th day of spraying treatment. Compared with the control groups (L0 and H0), NaCl spraying significantly increased dry matter and plant water content by 38.6% (L5)-50.2% (L10) and 20.8% (L5)-52.2% (L10) in L zone, 8.9% (H5)-23.3% (H10) and 8.7% (H5)-10.1% (H10) in H zone, respectively. The treatment of 10 mmol·L-1 NaCl (L10 and H10) under both temperature regimes increased dry matter accumulation and plant water content than other treatments. Nevertheless, the highest normalized strong seedling index (SI) with the highest stomatal conductance (gs) and photosynthetic rate (Pn) was only found in L5 treatment. L10 treatment promoted foliar expansion much more than H10 treatment. In addition, foliar spraying NaCl with concentrations from 5 mmol·L-1 to 10 mmol·L-1 under both temperature regimes significantly increased the accumulation of soluble sugar, free amino acids and soluble protein, which were preferentially allocated to the stem or root of cucumber seedlings. Results of two-way ANOVA showed significant effects of both temperature and NaCl concentration on dry biomass, leaf area, Pn, plant water content, SI, gs and free amino acid content. On the contrary, there were significant interactions between temperature and NaCl concentration in affecting plant water content, SI, gs and free amino acid content (except leaf). In conclusion, foliar spraying with 5-10 mmol L-1 NaCl could promote growth and physiological indices of cucumber seedlings, with the effect being higher under low temperature regime. More importantly, foliar spraying of proper concentration (L5 and H10) of NaCl could stimulate biomass accumulation more than water retention in cucumber seedlings, which would provide a relevant breeding target for high water-use efficiency in cucumber.

[Effects of bagging on light use efficiency of tomato fruit photosystem II].

In a greenhouse experiment, white laminating bags were applied to bag the tomato cultivar 'Baoluota' fruits, with the absorption spectra and chlorophyll fluorescence parameters of the fruits measured by optical spectrometer and Mini-Imaging-Pam after different bagging time, aimed to investigate the effects of bagging on the light use efficiency of photosystem II of the fruits. In the first 20 days of bagging, no significant effects of bagging were observed on the chlorophyll a (Chl a) content and the maximum quantum yield of PS II (Fv/Fm) of the fruits, but the relative absorption coefficient (A(670/780)) and the effective quantum yield of PS II (Y(II)) were reduced, compared with the control. In this period, the regulatory energy dissipation of PS II played, an important role. After then, the Chl a and Chl b contents of bagged fruits decreased markedly, but the Fv/Fm, Y(II), and A(670/780) had no significant differences with the control. On the 40th day of bagging, the Chl a and Chl b contents of bagged fruits decreased by 35.2% and 52.8%, but the Fv/Fm and Y(II) increased by 24.5% and 35.4%, respectively, suggesting that at this time, the PS II of bagged tomato fruits had a higher light use efficiency, which provided energy foundation for the earlier ripening of the bagged fruits via further reducing the quantum yield of non-regulatory energy dissipation (Y(NO)).

[Toxicological effects of omethoate on leaf photosystem II of cole].

After spraying different concentrations of two brands pesticide omethoate on cole (Brassica campestris L.) leaves, the leaf chlorophyll a fluorescence transients were measured by a Plant Efficiency Analyzer (PEA), and the toxicological effects and rudimental dynamic courses of omethoate on the leaf photosystem II (PS II) were investigated by JIP-test. The results showed that after spraying omethoate except at the concentration of 0.50% , the maximal efficiency of photochemistry (F(v)/F(m)) did not have a remarkable change. However, with increasing omethoate concentration, the minimal fluorescence F(o), maximal fluorescence F(m), relative variable fluorescence at the J-step (V(J)), and electron transport flux perreactive center in PS II (ET(o)/RC) increased remarkably, but psi(o), the efficiency that a trapped exciton in PS ]I moved an electron into the electron transport chain beyond Q(A)-, decreased remarkably. The test two brands of pesticide omethoate had almost alike effects on the PS II of cole, and the residual effect of the pesticide was the strongest at the third day after spraying and petered out from the ninth to twelfth day. The main targets of omethoate on the PS II of cole could be listed as promoting the reduction from Q(A) to Q(A) (-) (increasing of V(J)) and the electron transmission from Q(A) (-) to Q(B) (increasing of ET(o)/RC).